Résumé: The building stock in most historical urban areas in Algeria consists of old masonry buildings which are characterized by the rather high vulnerability. In that respect, to reduce the seismic risk there is a requirement for strategic urban planning and urban management policies. This paper focuses on the assessment of the seismic vulnerability using the RISK-UE methodology, namely the mechanical method LM2, which is adopted and applied to fit the Algerian urban features. In order to implement the RISK-UE LM2 methodology, an old urban center in Annaba city is chosen as a pilot area. Almost, the majority of the structures are unreinforced masonry buildings. In total 226 buildings were assessed, which are typical not only for this region but can be found in many other medium-sized Algerian urban environments. Three scenarios that take into account various values of the peak ground accelerations (PGA) are elaborated. Two scenarios use PGAs issued from an existing probabilistic seismic hazard analysis (PSHA) of Annaba city for 100 and 475 return periods. The third PGA for the last scenario is taken from the Algerian seismic code (RPA99/2003). In order to highlight the degree of vulnerability and risk of the studied masonry buildings, a comparison between the three seismic scenarios is presented in detail for each building’s typology. The obtained seismic vulnerability outcomes offer a great prospect to provide recommendations for making correct decisions to reduce the seismic risk and conduct adequate emergency planning in Algerian urban areas.

Résumé: The existence of several magnitude scales in the compiled earthquake catalogs of a specific region has made the development of regional relations connecting magnitude scales a necessity, especially for creating a homogeneous seismic catalog in which all magnitudes should be converted to a preferred magnitude scale. To consistently estimate all magnitude ranges and avoid the saturation problem for large earthquakes, the preference is always given to the moment magnitude Mw scale, wherein the most complete and reliable catalog used worldwide is the Global Centroid Moment Tensor (GCMT). However, to our knowledge, no study has yielded regional (in Algeria) relationships for converting different magnitudes to the moment magnitude (Mw,GCMT). The main reason is typically due to the lack of data pairs of different magnitude scales with Mw (GCMT). To overcome this issue, in this research paper, the moment magnitudes data used for northern Algeria (the area bounded by 32° to 39° N and 3° W to 10° E) have been taken principally from the GCMT catalog and enhanced with the European–Mediterranean Regional Centroid Moment Tensor catalogs RCMT and ZUR-CMT. Regarding this latter, it has been demonstrated in the literature that for the Mediterranean regions, a minor correction should be addressed before merging its data with the GCMT and RCMT catalogs, which are perfectly correlated. To accomplish this task, the magnitude scales tested against Mw are the surface wave magnitude, MS, and the body wave magnitude mb issued from the international seismological sources of ISC and NEIC for the same boundaries. As long as the earthquake magnitudes, in general, are affected by errors of comparable size, the best and most reliable regression method that considers the errors in both dependent and independent variables for linear conversion problems is the General Orthogonal Regression, which is adopted and applied herein to develop the regional relations.

Résumé: Nowadays, studying the behaviour of the old masonry structures is a challenging scope, wherein the knowledge of their material's mechanical properties is a preliminary input for their modelling purposes. Several methods can estimate these properties. On the one hand, unfortunately for the Algerian case, often these estimation methods could not be carried out, which led to the absence of scientific regulations and databases of the historical materials. On the other hand, the Algerian historical buildings stock needs urgent intervention and analysis for its conservation and preservation due to the deterioration state. In this context, the current research paper attempts to review the methods available in the literature used worldwide to evaluate the material properties of old masonry buildings through a deep comparison of scientific sources aiming at finding a possible and reliable way to determine the mechanical features of historical masonry constructions in Algeria.

Résumé: Hitherto, considerable research has been developed on the city scale to estimate the seismic hazard in terms of peak ground acceleration (PGA), which could be a valuable tool for the assessment of the building vulnerability using mechanical approaches. However, as material properties and dynamic characteristics are commonly unavailable to define detailed models for large-scale analysis, mechanical methods cannot be applied building-by-building. The only way to perform this task is by correlating the mechanical method with a macroseismic approach, which can be highly useful when only structural and geometrical surveys are available. In this context, this research aims to develop a simplified mechanical approach to assess the seismic vulnerability and the probability of damage of the Algerian masonry buildings at a large scale using a general structural data survey and in the presence of the seismic hazard in terms of PGA or spectral values. Accordingly, an existing macroseismic method derived from the GNDT II approach was correlated with the mechanical N2 method, which is herein adapted and applied to fit the features of the Algerian masonry buildings. This nonlinear method identifies the performance of buildings by means of “performance point,” referred to as the intersection between the earthquake demand curve, built here according to the Algerian seismic code (RPA 99/version 2003), and the capacity curve of an equivalent nonlinear S.D.O.F. system. For the implementation of the proposed approach, a total of 380 masonry buildings located in Annaba City (North-east in Algeria) were assessed. The fragility and the probability of damage results of the building stock were obtained through a comparison between the application of the vulnerability index method and the simplified mechanical approach for different seismic scenarios.

Résumé: Generally, buried steel pipes are designed for good transverse behavior by neglecting soil–structure interaction effect. Steel pipelines are also usually designed to prevent from the important failure mode of buckling. However, the design of this type of structures does not normally consider the uncertainties in soil and structural properties. To address the above issues, the paper estimates the uncertainties in terms of the coefficient of variation of critical buckling displacement, CVw using subgrade reaction theory (Winkler model) and first-order second-moment (FOSM) method. Two cases of boundary conditions have been considered in this study. In the first case, CVw is calculated within an infinitely thick soil as a function of uncertainty of subgrade reaction modulus (Ks). In the second case, CVw is calculated in a thick soil cylinder as a function of the uncertainty of the effective subgrade reaction modulus (K′S). Furthermore, the uncertainty of pipe flexibility (Sf) is also taken into account in the two cases. Uncertainty calculations by the FOSM method are then validated with those obtained from traditional Monte Carlo simulations.

Résumé: The failure of civil engineering systems is a consequence of decision making under uncertain conditions. Generally, buried flexible pipes are designed for their transversal behavior to prevent from the important failure mode of buckling. However, the interaction effects between soil and pipe are neglected and the uncertainties in their properties are usually not considered in pipe design. In this regard, the present research paper evaluates the effects of these uncertainties on the uncertainty of the critical buckling hoop force of flexible pipes shallowly buried using the subgrade reaction theory (Winkler model) and First-Order Second-Moment (FOSM) method. The results show that the structural uncertainties of the studied pipes and those of the soil properties have a significant effect on the uncertainty of the critical buckling hoop force, and therefore taking into account these latter in the design of the shallowly flexible pipes for their buckling behavior is required.

Résumé: Seismic vulnerability analysis of historical masonry buildings, addressed to earthquake emergency management and protection strategy planning, requires large-scale vulnerability and damage assessment. In this sense, two seismic vulnerability index methods and damage estimation have been adapted and applied to a pilot-scale urban area located in Annaba city (Algeria). The first method is based on the EMS-98 building typologies, and the second is based on the Italian GNDT approach. To accomplish this task, the authors employed an existing data survey, which, however, was not originally developed for seismic purposes. It was used herein to provide input to the vulnerability methods. The main goal of this research is not only to assess the seismic vulnerability and expected damage within Annaba, but also to adapt the two mentioned approaches to the existing data survey, aiming to use such nonspecific building database and to study the possibility of its application for seismic risk estimation in similar regions. The results obtained from the application of these two methods were integrated and compared using a geographic information system, proving that the vulnerability of the buildings surveyed in Annaba is significant, and therefore risk mitigation efforts and public awareness are required.